2010/2/23 Jonas Almström Duregård
Hi Rafael,
I assume you will perform this operation on some very large lists, or performance would not be an issue. Have you tested if your optimized version is better than your initial one?
You should compare your implementation against something like this:
import qualified Data.Set as Set noneRepeated :: (Ord a) => [a] -> Bool noneRepeated = accum Set.empty where accum _ [] = True accum s (x:xs) | Set.member x s = False | otherwise = accum (Set.insert x s) xs
Also there is some discussion about the nub function that relates to this topic, e.g. http://buffered.io/2008/07/28/a-better-nub/.
/Jonas
Or better yet, http://www.haskell.org/pipermail/libraries/2008-October/010778.html Much more thorough and practical w/r/t to actually getting faster nubs in the libraries. -- gwern